Aeronautic structures are designed in an optimal way to minimize weight and maximize strength. This way usually involves the use of a skin reinforced by some stiffening elements. Therefore, in the case of a fuselage, it is very common to have the skin stiffened by frames and stringers. The use of composite materials in the manufacturing of these elements is increasing, because of their better mechanical properties and their lower weight. Nevertheless, the manufacturing of complex elements, such as stringers that may change their size and thickness, their curvature and/or orientation, entail several drawbacks, as these changes are not easily followed by the traditional mould-and-plate machines.
The state of the art comprises several methods of manufacturing straight stringers, such as those described in US Pub. No. 2006/0231981A and WO 2012/062828A, but they are not suitable to manufacture non-straight stringers, because of the steps of the methods and the features of the machines implementing such methods. It would also be impossible to adapt said methods to non-straight stringers, as in such complex manufacturing process, wrinkles may appear, causing the non-validity of the final piece.
In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.